$A$ thermopile bolometer is used to detect:

The spectrum of black body radiation is a ...... .

If a black body at $400 \ K$ surrounded by atmosphere at $300 \ K$ has a rate of cooling '$R_0$',the same body at $900 \ K$,surrounded by the same atmosphere,will have a rate of cooling nearly:

Consider black body radiation in a cubical box at absolute temperature $T$. If the length of each side of the box is doubled and the temperature of the walls of the box and that of the radiation is halved, then the total energy

An ideal black body at room temperature is thrown into a furnace. It is observed that:

When red glass is heated in a dark room,it will appear: